Easily transportable devices with wireless telecommunications capabilities, such as mobile telephones, personal digital assistants, handheld computers, and similar devices, will be referred to herein as user equipment (UE). The term “user equipment” may refer to a device and its associated Universal Integrated Circuit Card (UICC) that includes a Subscriber Identity Module (SIM) application, a Universal Subscriber Identity Module (USIM) application, or a Removable User Identity Module (R-UIM) application or may refer to the device itself without such a card. A UE might communicate with a second UE, some other element in a telecommunications network, an automated computing device such as a server computer, or some other device. A communications connection between a UE and another component might promote a voice call, a file transfer, or some other type of data exchange, any of which can be referred to as a call or a session.
As telecommunications technology has evolved, more advanced network access equipment has been introduced that can provide services that were not possible previously. This advanced network access equipment might include, for example, an enhanced node B (ENB) rather than a base station or other systems and devices that are more highly evolved than the equivalent equipment in a traditional wireless telecommunications system. Such advanced or next generation equipment may be referred to herein as long-term evolution (LTE) equipment. Later generation or future advanced equipment that designates access nodes, for example nodes that provide radio access network (RAN) connectivity to UEs, are also referred to herein by the term ENB.
Some UEs have the capability to communicate in a packet switched mode, wherein a data stream representing a portion of a call or session is divided into packets that are given unique identifiers. The packets might then be transmitted from a source to a destination along different paths and might arrive at the destination at different times. Upon reaching the destination, the packets are reassembled into their original sequence based on the identifiers. Voice over Internet Protocol (VoIP) is a well-known system for packet switched-based voice communication over the Internet. The term “VoIP” will refer herein to any packet switched voice call connected via the Internet, regardless of the specific technology that might be used to make the call.
For a wireless VoIP call, the signal that carries data between a UE and an ENB can have a specific set of frequency, code, and time parameters and other characteristics that might be specified by the ENB. A connection between a UE and an ENB that has a specific set of such characteristics can be referred to as a resource. An ENB typically establishes a different resource for each UE with which it is communicating at any particular time.
New wireless communications systems may employ multiple input multiple output (MIMO) communication techniques. MIMO involves one or both of the UE and the ENB concurrently using multiple antennas for transmitting and/or receiving. Depending upon the radio channel conditions, the multiple antennas may be employed to increase the throughput of the radio link between the UE and the ENB, for example by transmitting independent streams of data on each antenna, or to increase the reliability of the radio link between the UE and the ENB, for example by transmitting redundant streams of data on the multiple antennas. These different communications objectives may be obtained through spatial multiplexing in the first case and through spatial diversity in the second case. Receiving multiple concurrent transmissions from a multi-antenna transmitter by a multi-antenna receiver may involve complicated processing techniques and/or algorithms.